This invention relates to an elevator hoisting device for hoisting an elevator car by a linear motor including a stator on the primary side disposed on the side of a building served by the elevator car.
Known linear motors for hoisting an elevator car are divided into two types one of which has the stator forming a primary side thereof disposed on the side of the moving member such as the counter weight, and the other type of which has the stator disposed on the side of a building served by an associated elevator car. In either case, an elevator car is connected to one end of a rope trained over a sheave disposed adjacent to a ceiling of an associated hoistway and connected at the other end to a counter weight. Thus the rope hangs the elevator car and the counter weight in an balanced state.
In the one type of linear motors a secondary electrical conductor is disposed in electrically insulating relationship on one wall of the hoistway to extend substantially the entire a height of the hoistway so as to cause the stator on the counter weight to travel along the same with a predetermined small gap formed therebetween while the secondary conductor is supplied with electric power through an electrical conductor connected to the stator.
In the other type of linear motors a plurality of stators forming the primary side thereof are disposed in vertically aligned, spaced relationship on one wall of the hoistway, one for each floor of the building, so that a secondary conductor disposed on the counter weight travels along the aligned stators with predetermined equal small gap formed between the same and the stators.
Either type of linear motors is advantageous in that a penthouse located above the hoistway is low in height because the hoisting motor and the hoisting device are not disposed within the penthouse.
With the stator disposed on the side of the counter weight, there is also the advantage that only a single linear motor is required but it is difficult to realize a high current cable having a long lifetime in view of the supply of an electrical power to the moving member such as the counter weight. Furthermore the secondary electrically conductor must be disposed on the side of the building resulting in an economic disadvantage.
On the other hand, with the stator disposed on the side of the building, a plurality of stators must be disposed in vertically aligned, spaced relationship on the side of the building to extend substantially the entire height thereof resulting also in an economic disadvantage.
Accordingly, it is an object of the present invention to eliminate the difficulty and disadvantages of the prior art practice as described above by the provision of an elevator hoisting device for driving an elevator car by a linear motor including no electrical conductor for supplying an electrical power to an associated moving member and capable of decreasing the number of the components thereof disposed on the side of a building served by an associated elevator car.